Modern electronic devices with a software operating system and a display often require a text input function but lack a full typewriter-style keyboard. A number of ersatz solutions have been developed that allow text input by means of a selection of letters with a cursor.
The most simple solution consists of a letter set shown on a display, with a cursor that can be controlled in two or four directions with a joystick or with keys. In order to advance the cursor by several positions, the keys have to be pressed several times accordingly. A further developed solution on this basis allows to keep the keys or the joystick activated for a certain minimum delay, leading to an automatic movement of the cursor in specified time intervals (auto-repeat function).
In order to move the cursor over longer distances, the speed of the cursor movement can be increased gradually (acceleration).
Touch screens, digitizing tablets and sensor strips allow to position a cursor directly at the desired position.
Predictive Text Input can guess a complete input sequence from a reduced information (9 keys instead of 26) on the basis of dictionary. This solution is in common use with mobile phones.
While the solution with two cursor keys is simple to manufacture and easy to learn, it requires numerous key presses or delays for each input character, so it is only accepted as a makeshift solution.
The cursor control with auto-repeat resp. acceleration makes it easier to traverse longer distances. The fast movement, however, leads to the common situation that the cursor surpasses the target so that the cursor position must be corrected tediously. This is because it is impossible to slow down the cursor movement.
While touch screens, digitizing tablets and sensor strips allow the direct selection of a cursor position, the large number of input alternatives leads to errors such as unintentionally selecting a position directly adjacent to the desired target position.
Predictive text input improves data input with numeric keypads significantly, as long as the input is limited to the vocabulary of its dictionary. In order to allow other input sequences, predictive text input must be turned off.
The known text input functions with a cursor control make use of a cursor with a constant size as well as targets (letter sets) with an identical size. Only predictive text input limits the possible input sequences to those that are assumed on the basis of an electronic dictionary.
Words of natural language contain some redundancy, i.e. after any letter only specific subsequent letters are possible to form meaningful words. For example, in the English and German languages words beginning with “Qua” often continue with a “d”, “n” or “r”, but not with an “a” or “q”.
The well-known and existing text input cursor control systems offer numerous letters for a selection, although these cannot be used for meaningful words at all. On the other side, predictive text input limits input sequences to words in a dictionary, although other letter sequences may be required for name or address information.
A procedure to support text entry by selecting letters with a cursor from a list should function with various cursor control hardware. It should also allow rapid input without limiting the vocabulary as predictive systems do.
The aim of the invention is to design a system for text entry by selecting letters from a list with a cursor in a user-friendly way, so that users do not have to memorize special input sequences and anybody can use it without special training.